The SNP started it with the Scottish referendum, Labour have joined in with an election pledge, and now the Coalition have jumped aboard the teenage franchise bandwagon by allowing an amendment to the Wales Bill which will give Welsh 16-year-olds the vote on tax-raising powers for the Welsh Assembly.

The arguments for lowering the voting age are so puerile that they would frankly embarrass, well, a 16-year-old. Campaigners tend to trot out the following: that 16-year-olds can “fight and die for the country” (stated by, amongst others, former Labour MEP now Baroness Morgan). Or that they can pay taxes, get married, and “sleep with their MPs but not vote for them” (an argument memorably put forward on the floor of the House of Commons by someone from the Youth Parliament).

Yes, you can join the Army at 16 as a Junior Soldier, although only with parental permission. You cannot under any circumstances be put into a war zone and asked to fight and die for your country until you are 18. This is a matter of international, as well as national, law. It is also prominently stated on the Army website – something that campaigners have never bothered to check

Taxes? You can pay them at any age at all if you earn the money. Scions of the very wealthy with trust funds, teenage stars or actors will pay them well before reaching 16. If eligibility to pay tax is a qualification for the vote, then it will not be long before MPs have to start canvassing toddlers. If the likelihood of paying taxes is the criteria, then 18 is still generous. According to a recent Parliamentary question, less than 4 per cent of 16 to 18-year-olds actually earn enough to pay income tax.

This leaves us with sex and marriage. 16-year-olds may be able to have sex with anyone, but anyone cannot have sex with 16-year-olds. Those with a duty of care to young people – teachers, youth workers and, presumably, MPs – would be breaking the law if they had sex with someone under the age of 18 because the law recognises that 16 to 18-year-olds could be vulnerable to predatory behaviour.

Marriage, like the Army, cannot be done without parental permission before 18. But the last Labour government raised the age at which you can bring a spouse into the country from outside the EU to 21. They did so because evidence suggests that, every year, large numbers of teenage girls from certain Asian communities are taken abroad and forced into marriage.

Sadly, following a legal challenge, the Supreme Court struck down the law and reversed the age for marrying foreign spouses back to 18.

This should ring alarm bells for campaigners seeking to reducing the voting age. By doing so, they will strengthen the argument that adulthood begins at 16 and open up a Pandora’s box of unintended consequences.

How long will it take for an aggrieved parent to demand that his 16-year-old should be able marry a foreign national who she has never met? How long before a teacher convicted of sleeping with a 16-year-old pupil takes a case to the Supreme Court arguing that the pupil was legally an adult? There will certainly be plenty of newsagents who will wonder why MPs can believe that 16-year-olds are old enough to be given the vote, but not old enough to be sold cigarettes or fireworks.

I have spent 9 years working as Special Constable in London and dealt with numerous juveniles who are afforded protections that would never be extended to an adult. A 16-year-old I found begging in a station was taken in given a cup of tea and some food, and then reunited with her parents. An 18-year-old would simply have been asked to leave.

I once arrested a 16-year-old who was carrying a gun. He was not imprisoned because of his age. Another teenager under arrest was not locked in a cell or handcuffed because of her age, enabling her to attack myself and various other officers. No action was taken. 16 and 17-year-olds who are arrested cannot be interviewed without an adult present and, if they are convicted, will be treated far more leniently than an 18-year-old.

But, despite the irritation it has caused me, I am glad that the law gives extra protection to 16 and 17-year-olds who are on the brink of adulthood, and I despise the hypocrisy of those who want to lower the franchise. On voting rights they describe 16-year-olds as “adults”; on justice matters the same people describe 16-year-olds as children deserving of even more leniency than they already get.

There are many 16-year-olds who would be more than capable of making an informed decision about whom to vote for, but we cannot legislate for individuals. Instead we enable 16 to 18-year-olds to ease into the responsibilities which at 18, with the right to vote, they have to accept in full.

Lowering the franchise would not undermine democracy, but it would undermine the protections which we currently give to 16 and 17-year-olds. It is time for its supporters to grow up!